Diagnostic

The word diagnostic, when used as a noun, refers to any on-board test run by the vehicle PCM. A diagnostic is simply a test run on a system or component in order to determine if the system or the component is operating according to specifications. The following list defines the major vehicle on-board diagnostics. Depending on the emission requirements in the area of vehicle sale, certain diagnostics listed below may not apply:
^ Misfire
^ Oxygen sensors
^ Oxygen sensor heaters
^ Exhaust Gas Recirculation (EGR)
^ Catalyst monitoring